linux/arch/x86/ia32/ia32entry.S

/*
 * Compatibility mode system call entry point for x86-64. 
 * 		
 * Copyright 2000-2002 Andi Kleen, SuSE Labs.
 */		 

#include <asm/dwarf2.h>
#include <asm/calling.h>
#include <asm/asm-offsets.h>
#include <asm/current.h>
#include <asm/errno.h>
#include <asm/ia32_unistd.h>	
#include <asm/thread_info.h>	
#include <asm/segment.h>
#include <asm/irqflags.h>
#include <asm/asm.h>
#include <asm/smap.h>
#include <linux/linkage.h>
#include <linux/err.h>

/* Avoid __ASSEMBLER__'ifying <linux/audit.h> just for this.  */
#include <linux/elf-em.h>
#define AUDIT_ARCH_I386		(EM_386|__AUDIT_ARCH_LE)
#define __AUDIT_ARCH_LE	   0x40000000

#ifndef CONFIG_AUDITSYSCALL
#define sysexit_audit ia32_ret_from_sys_call
#define sysretl_audit ia32_ret_from_sys_call
#endif

	.section .entry.text, "ax"

	/* clobbers %rax */
	.macro  CLEAR_RREGS _r9=rax
	xorl 	%eax,%eax
	movq	%rax,R11(%rsp)
	movq	%rax,R10(%rsp)
	movq	%\_r9,R9(%rsp)
	movq	%rax,R8(%rsp)
	.endm

	/*
	 * Reload arg registers from stack in case ptrace changed them.
	 * We don't reload %eax because syscall_trace_enter() returned
	 * the %rax value we should see.  Instead, we just truncate that
	 * value to 32 bits again as we did on entry from user mode.
	 * If it's a new value set by user_regset during entry tracing,
	 * this matches the normal truncation of the user-mode value.
	 * If it's -1 to make us punt the syscall, then (u32)-1 is still
	 * an appropriately invalid value.
	 */
	.macro LOAD_ARGS32 _r9=0
	.if \_r9
	movl R9(%rsp),%r9d
	.endif
	movl RCX(%rsp),%ecx
	movl RDX(%rsp),%edx
	movl RSI(%rsp),%esi
	movl RDI(%rsp),%edi
	movl %eax,%eax			/* zero extension */
	.endm
	
	.macro CFI_STARTPROC32 simple
	CFI_STARTPROC	\simple
	CFI_UNDEFINED	r8
	CFI_UNDEFINED	r9
	CFI_UNDEFINED	r10
	CFI_UNDEFINED	r11
	CFI_UNDEFINED	r12
	CFI_UNDEFINED	r13
	CFI_UNDEFINED	r14
	CFI_UNDEFINED	r15
	.endm

#ifdef CONFIG_PARAVIRT
ENTRY(native_usergs_sysret32)
	swapgs
	sysretl
ENDPROC(native_usergs_sysret32)

ENTRY(native_irq_enable_sysexit)
	swapgs
	sti
	sysexit
ENDPROC(native_irq_enable_sysexit)
#endif

/*
 * 32bit SYSENTER instruction entry.
 *
 * SYSENTER loads ss, rsp, cs, and rip from previously programmed MSRs.
 * IF and VM in rflags are cleared (IOW: interrupts are off).
 * SYSENTER does not save anything on the stack,
 * and does not save old rip (!!!) and rflags.
 *
 * Arguments:
 * eax  system call number
 * ebx  arg1
 * ecx  arg2
 * edx  arg3
 * esi  arg4
 * edi  arg5
 * ebp  user stack
 * 0(%ebp) arg6
 *
 * This is purely a fast path. For anything complicated we use the int 0x80
 * path below. We set up a complete hardware stack frame to share code
 * with the int 0x80 path.
 */
ENTRY(ia32_sysenter_target)
	CFI_STARTPROC32	simple
	CFI_SIGNAL_FRAME
	CFI_DEF_CFA	rsp,0
	CFI_REGISTER	rsp,rbp

	/*
	 * Interrupts are off on entry.
	 * We do not frame this tiny irq-off block with TRACE_IRQS_OFF/ON,
	 * it is too small to ever cause noticeable irq latency.
	 */
	SWAPGS_UNSAFE_STACK
	movq	PER_CPU_VAR(cpu_tss + TSS_sp0), %rsp
	ENABLE_INTERRUPTS(CLBR_NONE)

	/* Construct iret frame (ss,rsp,rflags,cs,rip) */
 	movl	%ebp,%ebp		/* zero extension */
	pushq_cfi $__USER32_DS
	/*CFI_REL_OFFSET ss,0*/
	pushq_cfi %rbp
	CFI_REL_OFFSET rsp,0
	pushfq_cfi
	/*CFI_REL_OFFSET rflags,0*/
	movl	ASM_THREAD_INFO(TI_sysenter_return, %rsp, 3*8), %r10d
	CFI_REGISTER rip,r10
	pushq_cfi $__USER32_CS
	/*CFI_REL_OFFSET cs,0*/
	movl	%eax, %eax
	/* Store thread_info->sysenter_return in rip stack slot */
	pushq_cfi %r10
	CFI_REL_OFFSET rip,0
	/* Store orig_ax */
	pushq_cfi %rax
	/* Construct the rest of "struct pt_regs" */
	cld
	ALLOC_PT_GPREGS_ON_STACK
	SAVE_C_REGS_EXCEPT_R891011
	/*
	 * no need to do an access_ok check here because rbp has been
	 * 32bit zero extended
	 */
	ASM_STAC
1:	movl	(%rbp),%ebp
	_ASM_EXTABLE(1b,ia32_badarg)
	ASM_CLAC

	/*
	 * Sysenter doesn't filter flags, so we need to clear NT
	 * ourselves.  To save a few cycles, we can check whether
	 * NT was set instead of doing an unconditional popfq.
	 */
	testl $X86_EFLAGS_NT,EFLAGS(%rsp)
	jnz sysenter_fix_flags
sysenter_flags_fixed:

	orl     $TS_COMPAT, ASM_THREAD_INFO(TI_status, %rsp, SIZEOF_PTREGS)
	testl   $_TIF_WORK_SYSCALL_ENTRY, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
	CFI_REMEMBER_STATE
	jnz  sysenter_tracesys
	cmpq	$(IA32_NR_syscalls-1),%rax
	ja	ia32_badsys
sysenter_do_call:
	/* 32bit syscall -> 64bit C ABI argument conversion */
	movl	%edi,%r8d	/* arg5 */
	movl	%ebp,%r9d	/* arg6 */
	xchg	%ecx,%esi	/* rsi:arg2, rcx:arg4 */
	movl	%ebx,%edi	/* arg1 */
	movl	%edx,%edx	/* arg3 (zero extension) */
sysenter_dispatch:
	call	*ia32_sys_call_table(,%rax,8)
	movq	%rax,RAX(%rsp)
	DISABLE_INTERRUPTS(CLBR_NONE)
	TRACE_IRQS_OFF
	testl	$_TIF_ALLWORK_MASK, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
	jnz	sysexit_audit
sysexit_from_sys_call:
	andl    $~TS_COMPAT,ASM_THREAD_INFO(TI_status, %rsp, SIZEOF_PTREGS)
	/* clear IF, that popfq doesn't enable interrupts early */
	andl	$~0x200,EFLAGS(%rsp)
	movl	RIP(%rsp),%edx		/* User %eip */
	CFI_REGISTER rip,rdx
	RESTORE_RSI_RDI
	/* pop everything except ss,rsp,rflags slots */
	REMOVE_PT_GPREGS_FROM_STACK 3*8
	xorq	%r8,%r8
	xorq	%r9,%r9
	xorq	%r10,%r10
	xorq	%r11,%r11
	popfq_cfi
	/*CFI_RESTORE rflags*/
	popq_cfi %rcx				/* User %esp */
	CFI_REGISTER rsp,rcx
	TRACE_IRQS_ON
	/*
	 * 32bit SYSEXIT restores eip from edx, esp from ecx.
	 * cs and ss are loaded from MSRs.
	 */
	ENABLE_INTERRUPTS_SYSEXIT32

	CFI_RESTORE_STATE

#ifdef CONFIG_AUDITSYSCALL
	.macro auditsys_entry_common
	movl %esi,%r8d			/* 5th arg: 4th syscall arg */
	movl %ecx,%r9d			/*swap with edx*/
	movl %edx,%ecx			/* 4th arg: 3rd syscall arg */
	movl %r9d,%edx			/* 3rd arg: 2nd syscall arg */
	movl %ebx,%esi			/* 2nd arg: 1st syscall arg */
	movl %eax,%edi			/* 1st arg: syscall number */
	call __audit_syscall_entry
	movl RAX(%rsp),%eax	/* reload syscall number */
	cmpq $(IA32_NR_syscalls-1),%rax
	ja ia32_badsys
	movl %ebx,%edi			/* reload 1st syscall arg */
	movl RCX(%rsp),%esi	/* reload 2nd syscall arg */
	movl RDX(%rsp),%edx	/* reload 3rd syscall arg */
	movl RSI(%rsp),%ecx	/* reload 4th syscall arg */
	movl RDI(%rsp),%r8d	/* reload 5th syscall arg */
	.endm

	.macro auditsys_exit exit
	testl $(_TIF_ALLWORK_MASK & ~_TIF_SYSCALL_AUDIT), ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
	jnz ia32_ret_from_sys_call
	TRACE_IRQS_ON
	ENABLE_INTERRUPTS(CLBR_NONE)
	movl %eax,%esi		/* second arg, syscall return value */
	cmpl $-MAX_ERRNO,%eax	/* is it an error ? */
	jbe 1f
	movslq %eax, %rsi	/* if error sign extend to 64 bits */
1:	setbe %al		/* 1 if error, 0 if not */
	movzbl %al,%edi		/* zero-extend that into %edi */
	call __audit_syscall_exit
	movq RAX(%rsp),%rax	/* reload syscall return value */
	movl $(_TIF_ALLWORK_MASK & ~_TIF_SYSCALL_AUDIT),%edi
	DISABLE_INTERRUPTS(CLBR_NONE)
	TRACE_IRQS_OFF
	testl %edi, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
	jz \exit
	CLEAR_RREGS
	jmp int_with_check
	.endm

sysenter_auditsys:
	auditsys_entry_common
	movl %ebp,%r9d			/* reload 6th syscall arg */
	jmp sysenter_dispatch

sysexit_audit:
	auditsys_exit sysexit_from_sys_call
#endif

sysenter_fix_flags:
	pushq_cfi $(X86_EFLAGS_IF|X86_EFLAGS_FIXED)
	popfq_cfi
	jmp sysenter_flags_fixed

sysenter_tracesys:
#ifdef CONFIG_AUDITSYSCALL
	testl	$(_TIF_WORK_SYSCALL_ENTRY & ~_TIF_SYSCALL_AUDIT), ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
	jz	sysenter_auditsys
#endif
	SAVE_EXTRA_REGS
	CLEAR_RREGS
	movq	$-ENOSYS,RAX(%rsp)/* ptrace can change this for a bad syscall */
	movq	%rsp,%rdi        /* &pt_regs -> arg1 */
	call	syscall_trace_enter
	LOAD_ARGS32  /* reload args from stack in case ptrace changed it */
	RESTORE_EXTRA_REGS
	cmpq	$(IA32_NR_syscalls-1),%rax
	ja	int_ret_from_sys_call /* sysenter_tracesys has set RAX(%rsp) */
	jmp	sysenter_do_call
	CFI_ENDPROC
ENDPROC(ia32_sysenter_target)

/*
 * 32bit SYSCALL instruction entry.
 *
 * 32bit SYSCALL saves rip to rcx, clears rflags.RF, then saves rflags to r11,
 * then loads new ss, cs, and rip from previously programmed MSRs.
 * rflags gets masked by a value from another MSR (so CLD and CLAC
 * are not needed). SYSCALL does not save anything on the stack
 * and does not change rsp.
 *
 * Note: rflags saving+masking-with-MSR happens only in Long mode
 * (in legacy 32bit mode, IF, RF and VM bits are cleared and that's it).
 * Don't get confused: rflags saving+masking depends on Long Mode Active bit
 * (EFER.LMA=1), NOT on bitness of userspace where SYSCALL executes
 * or target CS descriptor's L bit (SYSCALL does not read segment descriptors).
 *
 * Arguments:
 * eax  system call number
 * ecx  return address
 * ebx  arg1
 * ebp  arg2	(note: not saved in the stack frame, should not be touched)
 * edx  arg3
 * esi  arg4
 * edi  arg5
 * esp  user stack
 * 0(%esp) arg6
 *
 * This is purely a fast path. For anything complicated we use the int 0x80
 * path below. We set up a complete hardware stack frame to share code
 * with the int 0x80 path.
 */
ENTRY(ia32_cstar_target)
	CFI_STARTPROC32	simple
	CFI_SIGNAL_FRAME
	CFI_DEF_CFA	rsp,0
	CFI_REGISTER	rip,rcx
	/*CFI_REGISTER	rflags,r11*/

	/*
	 * Interrupts are off on entry.
	 * We do not frame this tiny irq-off block with TRACE_IRQS_OFF/ON,
	 * it is too small to ever cause noticeable irq latency.
	 */
	SWAPGS_UNSAFE_STACK
	movl	%esp,%r8d
	CFI_REGISTER	rsp,r8
	movq	PER_CPU_VAR(kernel_stack),%rsp
	ENABLE_INTERRUPTS(CLBR_NONE)

	ALLOC_PT_GPREGS_ON_STACK 6*8 /* 6*8: space for orig_ax and iret frame */
	SAVE_C_REGS_EXCEPT_RCX_R891011
	movl 	%eax,%eax	/* zero extension */
	movq	%rax,ORIG_RAX(%rsp)
	movq	%rcx,RIP(%rsp)
	CFI_REL_OFFSET rip,RIP
	movq	%rbp,RCX(%rsp) /* this lies slightly to ptrace */
	movl	%ebp,%ecx
	movq	$__USER32_CS,CS(%rsp)
	movq	$__USER32_DS,SS(%rsp)
	movq	%r11,EFLAGS(%rsp)
	/*CFI_REL_OFFSET rflags,EFLAGS*/
	movq	%r8,RSP(%rsp)
	CFI_REL_OFFSET rsp,RSP
	/* iret stack frame is complete now */
	/*
	 * no need to do an access_ok check here because r8 has been
	 * 32bit zero extended
	 */
	ASM_STAC
1:	movl	(%r8),%r9d
	_ASM_EXTABLE(1b,ia32_badarg)
	ASM_CLAC
	orl     $TS_COMPAT, ASM_THREAD_INFO(TI_status, %rsp, SIZEOF_PTREGS)
	testl   $_TIF_WORK_SYSCALL_ENTRY, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
	CFI_REMEMBER_STATE
	jnz   cstar_tracesys
	cmpq $IA32_NR_syscalls-1,%rax
	ja  ia32_badsys
cstar_do_call:
	/* 32bit syscall -> 64bit C ABI argument conversion */
	movl	%edi,%r8d	/* arg5 */
	/* r9 already loaded */	/* arg6 */
	xchg	%ecx,%esi	/* rsi:arg2, rcx:arg4 */
	movl	%ebx,%edi	/* arg1 */
	movl	%edx,%edx	/* arg3 (zero extension) */
cstar_dispatch:
	call *ia32_sys_call_table(,%rax,8)
	movq %rax,RAX(%rsp)
	DISABLE_INTERRUPTS(CLBR_NONE)
	TRACE_IRQS_OFF
	testl $_TIF_ALLWORK_MASK, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
	jnz sysretl_audit
sysretl_from_sys_call:
	andl $~TS_COMPAT, ASM_THREAD_INFO(TI_status, %rsp, SIZEOF_PTREGS)
	RESTORE_RSI_RDI_RDX
	movl RIP(%rsp),%ecx
	CFI_REGISTER rip,rcx
	movl EFLAGS(%rsp),%r11d
	/*CFI_REGISTER rflags,r11*/
	xorq	%r10,%r10
	xorq	%r9,%r9
	xorq	%r8,%r8
	TRACE_IRQS_ON
	movl RSP(%rsp),%esp
	CFI_RESTORE rsp
	/*
	 * 64bit->32bit SYSRET restores eip from ecx,
	 * eflags from r11 (but RF and VM bits are forced to 0),
	 * cs and ss are loaded from MSRs.
	 * (Note: 32bit->32bit SYSRET is different: since r11
	 * does not exist, it merely sets eflags.IF=1).
	 */
	USERGS_SYSRET32

#ifdef CONFIG_AUDITSYSCALL
cstar_auditsys:
	CFI_RESTORE_STATE
	movl %r9d,R9(%rsp)	/* register to be clobbered by call */
	auditsys_entry_common
	movl R9(%rsp),%r9d	/* reload 6th syscall arg */
	jmp cstar_dispatch

sysretl_audit:
	auditsys_exit sysretl_from_sys_call
#endif

cstar_tracesys:
#ifdef CONFIG_AUDITSYSCALL
	testl $(_TIF_WORK_SYSCALL_ENTRY & ~_TIF_SYSCALL_AUDIT), ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
	jz cstar_auditsys
#endif
	xchgl %r9d,%ebp
	SAVE_EXTRA_REGS
	CLEAR_RREGS r9
	movq $-ENOSYS,RAX(%rsp)	/* ptrace can change this for a bad syscall */
	movq %rsp,%rdi        /* &pt_regs -> arg1 */
	call syscall_trace_enter
	LOAD_ARGS32 1	/* reload args from stack in case ptrace changed it */
	RESTORE_EXTRA_REGS
	xchgl %ebp,%r9d
	cmpq $(IA32_NR_syscalls-1),%rax
	ja int_ret_from_sys_call /* cstar_tracesys has set RAX(%rsp) */
	jmp cstar_do_call
END(ia32_cstar_target)
				
ia32_badarg:
	ASM_CLAC
	movq $-EFAULT,%rax
	jmp ia32_sysret
	CFI_ENDPROC

/*
 * Emulated IA32 system calls via int 0x80.
 *
 * Arguments:
 * eax  system call number
 * ebx  arg1
 * ecx  arg2
 * edx  arg3
 * esi  arg4
 * edi  arg5
 * ebp  arg6	(note: not saved in the stack frame, should not be touched)
 *
 * Notes:
 * Uses the same stack frame as the x86-64 version.
 * All registers except eax must be saved (but ptrace may violate that).
 * Arguments are zero extended. For system calls that want sign extension and
 * take long arguments a wrapper is needed. Most calls can just be called
 * directly.
 * Assumes it is only called from user space and entered with interrupts off.
 */

ENTRY(ia32_syscall)
	CFI_STARTPROC32	simple
	CFI_SIGNAL_FRAME
	CFI_DEF_CFA	rsp,5*8
	/*CFI_REL_OFFSET	ss,4*8 */
	CFI_REL_OFFSET	rsp,3*8
	/*CFI_REL_OFFSET	rflags,2*8 */
	/*CFI_REL_OFFSET	cs,1*8 */
	CFI_REL_OFFSET	rip,0*8

	/*
	 * Interrupts are off on entry.
	 * We do not frame this tiny irq-off block with TRACE_IRQS_OFF/ON,
	 * it is too small to ever cause noticeable irq latency.
	 */
	PARAVIRT_ADJUST_EXCEPTION_FRAME
	SWAPGS
	ENABLE_INTERRUPTS(CLBR_NONE)

	movl %eax,%eax
	pushq_cfi %rax		/* store orig_ax */
	cld
	/* note the registers are not zero extended to the sf.
	   this could be a problem. */
	ALLOC_PT_GPREGS_ON_STACK
	SAVE_C_REGS_EXCEPT_R891011
	orl $TS_COMPAT, ASM_THREAD_INFO(TI_status, %rsp, SIZEOF_PTREGS)
	testl $_TIF_WORK_SYSCALL_ENTRY, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
	jnz ia32_tracesys
	cmpq $(IA32_NR_syscalls-1),%rax
	ja ia32_badsys
ia32_do_call:
	/* 32bit syscall -> 64bit C ABI argument conversion */
	movl %edi,%r8d	/* arg5 */
	movl %ebp,%r9d	/* arg6 */
	xchg %ecx,%esi	/* rsi:arg2, rcx:arg4 */
	movl %ebx,%edi	/* arg1 */
	movl %edx,%edx	/* arg3 (zero extension) */
	call *ia32_sys_call_table(,%rax,8) # xxx: rip relative
ia32_sysret:
	movq %rax,RAX(%rsp)
ia32_ret_from_sys_call:
	CLEAR_RREGS
	jmp int_ret_from_sys_call

ia32_tracesys:
	SAVE_EXTRA_REGS
	CLEAR_RREGS
	movq $-ENOSYS,RAX(%rsp)	/* ptrace can change this for a bad syscall */
	movq %rsp,%rdi        /* &pt_regs -> arg1 */
	call syscall_trace_enter
	LOAD_ARGS32	/* reload args from stack in case ptrace changed it */
	RESTORE_EXTRA_REGS
	cmpq $(IA32_NR_syscalls-1),%rax
	ja  int_ret_from_sys_call	/* ia32_tracesys has set RAX(%rsp) */
	jmp ia32_do_call
END(ia32_syscall)

ia32_badsys:
	movq $0,ORIG_RAX(%rsp)
	movq $-ENOSYS,%rax
	jmp ia32_sysret

	CFI_ENDPROC
	
	.macro PTREGSCALL label, func
	ALIGN
GLOBAL(\label)
	leaq \func(%rip),%rax
	jmp  ia32_ptregs_common	
	.endm

	CFI_STARTPROC32

	PTREGSCALL stub32_rt_sigreturn, sys32_rt_sigreturn
	PTREGSCALL stub32_sigreturn, sys32_sigreturn
	PTREGSCALL stub32_execve, compat_sys_execve
	PTREGSCALL stub32_execveat, compat_sys_execveat
	PTREGSCALL stub32_fork, sys_fork
	PTREGSCALL stub32_vfork, sys_vfork

	ALIGN
GLOBAL(stub32_clone)
	leaq sys_clone(%rip),%rax
	mov	%r8, %rcx
	jmp  ia32_ptregs_common	

	ALIGN
ia32_ptregs_common:
	CFI_ENDPROC
	CFI_STARTPROC32	simple
	CFI_SIGNAL_FRAME
	CFI_DEF_CFA	rsp,SIZEOF_PTREGS
	CFI_REL_OFFSET	rax,RAX
	CFI_REL_OFFSET	rcx,RCX
	CFI_REL_OFFSET	rdx,RDX
	CFI_REL_OFFSET	rsi,RSI
	CFI_REL_OFFSET	rdi,RDI
	CFI_REL_OFFSET	rip,RIP
/*	CFI_REL_OFFSET	cs,CS*/
/*	CFI_REL_OFFSET	rflags,EFLAGS*/
	CFI_REL_OFFSET	rsp,RSP
/*	CFI_REL_OFFSET	ss,SS*/
	SAVE_EXTRA_REGS 8
	call *%rax
	RESTORE_EXTRA_REGS 8
	ret
	CFI_ENDPROC
END(ia32_ptregs_common)